AutoFill fills only clicked field when form was filled prior.

chrome/renderer/render_view.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/renderer/render_view.h"
 
 #include <algorithm>
 #include <string>
 #include <vector>
 
@@ skipping 2093 matching lines @@
   DCHECK_NE(0U, suggestions_count_);
 
   if (index == suggestions_count_ - 1) {
     // User selected 'AutoFill Options...'.
     Send(new ViewHostMsg_ShowAutoFillDialog(routing_id_));
   } else if (form_manager_.FormWithNodeIsAutoFilled(node) &&
              index == suggestions_count_ - 2) {
     // The form has been auto-filled, so give the user the chance to clear the
     // form.
     form_manager_.ClearFormWithNode(node);
+  } else if (form_manager_.FormWithNodeIsAutoFilled(node)) {
+    // Fill a specific field value.
+    // Cast away const'ness in this case where we're filling the element
+    // directly.
+    WebInputElement element = node.toConst<WebInputElement>();
+    element.setValue(value);
   } else {
+    // Fill the values for the whole form.
     QueryAutoFillFormData(node, value, label, AUTOFILL_FILL);
   }
 
   suggestions_count_ = 0;
 }
 
 void RenderView::didSelectAutoFillSuggestion(const WebKit::WebNode& node,
                                              const WebKit::WebString& value,
                                              const WebKit::WebString& label) {
   didClearAutoFillSelection(node);
@@ skipping 3124 matching lines @@
   webkit_glue::FormData form;
   const WebInputElement element = node.toConst<WebInputElement>();
   if (!form_manager_.FindFormWithFormControlElement(
           element, FormManager::REQUIRE_NONE, &form))
     return;
 
   autofill_action_ = action;
   Send(new ViewHostMsg_FillAutoFillFormData(
       routing_id_, autofill_query_id_, form, value, label));
 }